Analysis of ethylene oxide and 2-chloroethanol residues in food using GC-MS/MS

Importance of the topic

Ethylene oxide (EO) is widely used for sterilizing dry food commodities but poses mutagenic and carcinogenic risks at trace levels. Regulatory bodies require monitoring EO and its by-product 2-chloroethanol (2CE) in foods, with maximum residue limits as low as 0.02 mg/kg. Recent alerts in the European Rapid Alert System (RASFF) highlight the need for sensitive, reliable analytical methods.

Objectives and study overview

This work evaluates the performance of the Thermo Scientific™ TRACE™ 1610 gas chromatograph coupled to a TSQ™ 9610 triple quadrupole GC-MS/MS with Advance Electron Ionization (AEI) source. The goal is to demonstrate sensitivity, selectivity, linearity and long-term robustness for EO and 2CE analysis in various food matrices, following EU SANTE/11312/2021 quality control guidelines.

Methodology and instrumentation

A modified QuOil extraction protocol was performed on 3 g of sample using 10 mL aqueous acetonitrile (95:5). After centrifugation, dSPE clean-up (C18/PSA/MgSO4) was applied. Samples and standards were kept at 7 °C in a TriPlus™ RSH autosampler.

• GC system: TRACE 1610 with iConnect™ Programmable Temperature Vaporizing (PTV) injector and Siltek baffle liner.
• Column: TraceGOLD™ TG-624SilMS (30 m × 0.25 mm × 1.40 µm) with GuardGOLD™ pre-column.
• Carrier gas: helium, 1 mL/min.
• Temperature program: 45 °C (2 min) → 150 °C at 50 °C/min → 300 °C at 100 °C/min.
• MS/MS: TSQ 9610 triple quadrupole with AEI source at 270 °C, transfer line at 280 °C, argon collision gas.
• Monitoring transitions: EO 44→14 (20 eV), 44→29 (5 eV); 2CE 80→31 (5 eV), 80→43 (5 eV); internal standard 2CE-d4.

Results and discussion

Chromatographic separation on the TG-624SilMS column resolved EO from coeluting acetaldehyde by 0.14 min. With only 1 µL injection, limits of quantitation around 0.007 mg/kg in sample were consistently achieved. Calibration linearity spanned 0.007–16.5 mg/kg (R²>0.999) with back-calculated deviations within ±13% and compliant ion ratios (±30%).

An extended sequence of 230 injections over three days, interrupted only for septum change, showed stable internal standard response (RSD 8.8%) and retention time shifts <0.01 min. No maintenance or tuning was required.

Analysis of ten real food samples (spices, cereals, seeds) detected no EO residues; 2CE was found in all matrices at 0.005–0.12 mg/kg. Results agreed within 20% of values from an ISO/IEC 17025 accredited reference laboratory, with both external and internal standard calibrations yielding equivalent accuracy.

Benefits and practical applications

• High sensitivity and low injection volume reduce matrix load and maintenance frequency.
• Broad linear range accommodates variable residue levels without repeat analysis.
• Robust AEI source and column combination support long unattended sequences for high throughput.
• Compliance with EU SANTE guidelines ensures regulatory acceptance.

Future trends and applications

Advances in automated, cooled sample handling and microvolume injection promise further reduction of analyte loss for volatile residues. Integration with high-capacity autosamplers and expanded compound panels (e.g., other reactive epoxides) will extend applicability. Machine-learning-driven data processing may enhance selectivity and throughput for routine monitoring programs.

Conclusion

The TRACE 1610 GC with TSQ 9610 GC-MS/MS and AEI source delivers a sensitive, selective and robust workflow for quantifying EO and 2CE in food. The method meets low MRL requirements, offers wide linearity, and sustains prolonged sequences without maintenance, supporting high-volume regulatory and quality-control laboratories.

References

1. Dudkiewicz A, Dutta P, Kołożyn-Krajewska D. Eur Food Res Technol. 2022;doi:10.1007/s00217-022-04018-7
2. Kirman CR et al. J Toxicol Environ Health B Crit Rev. 2021;24(1):1–29.
3. European Commission RASFF notifications (Jan–Apr current year).
4. Regulation (EC) No 396/2005 on pesticide MRLs.
5. Commission Regulation (EU) 2015/868 amending MRLs for ethylene oxide.
6. SANTE/11312/2021: Analytical quality control and method validation procedures for pesticide residues analysis in food and feed.
7. EURL-SRM Analytical Observations Report: EO and 2CE by QuOil GC-MS/MS.